Dual format adhesive process for intermittently disrupting parallel lines of adhesive to form adhesive bands

ABSTRACT

A laminate is made by applying a plurality of parallel fine lines of adhesive to a first web, intermittently agitating the adhesive prior to deposition to intermingle the adhesive to form spaced apart bands extending across the fine lines, and then applying a second web over the adhesive to join the webs together. The intermittent cross bands prevent migration of particles and leakage along said fine lines. When diapers are made from the laminate, waistbands are formed in the areas of the cross bands. Apparatus is disclosed.

This application is a divisional of application Ser. No. 07/865,094,filed Apr. 8, 1992, now U.S. Pat. No. 5,382,312.

This invention relates to adhesive application for lamination and moreparticularly to adhesive applicators and methods for improved adhesiveapplication and products.

It is well known to adhere two webs or sheets together by applyingparallel beads or fine lines of adhesives to one web or sheet and thencombining the two webs or sheets so the adhesive can bind them together.One use of this technique is found in the manufacture of disposablediapers. These usually include a moisture impervious polyethylenebacking, and a non-woven, absorbent pad sometimes referred to as"fluff".

In making such diapers, parallel beads or fine lines of adhesive aredeposited in a machine direction onto a moving web of polyethylenebacking material. The non-woven web or fluff is laid on the plastic webso the elongated adhesive beads secure it to the backing. Leg holes arethen cut in the laminate and the diaper is otherwise finished. Such atechnique is described in U.S. Pat. No. 4,874,451, which is incorporatedherein by reference.

One of the difficulties in using such a technique in manufacturingdiapers is that the adhesive beads tend to define channels on thepolyethylene backing. Particles of super absorbent non-woven materialcan migrate through these channels to the diaper's leg holes or waistareas where they escape. The channels may lead to other problems such asleaking. Additional manufacturing treatment or components are requiredto seal off these channels.

It is also known in the diaper manufacturing industry to apply theadhesive to the plastic backing web in a "swirl" pattern, or in random"fibrous" depositions. Overlapping swirls could be applied, for example,by apparatus such as that disclosed in U.S. Pat. No. 4,983,109, which isincorporated herein by reference. Such swirl or fibrous adhesiveapplications provide a more "homogeneous" or continuous adhesive blanketand do not create the channels noted above. They thus provide continuousadhesion, both in the machine direction and in the cross-machinedirection across the backing. This inhibits moisture leaking or particlemigration. Also, these processes permit cooler deposition of hot meltadhesives on the plastic backing, thus avoiding burn through.Accordingly, the gage of the backing can be reduced, with attendant costsavings.

Nevertheless, the parallel bead process does provide certain beneficialadherance and process characteristics not obtained by the "swirling"process. For example, the beads remain at a somewhat higher temperaturewhen applied and in certain applications generate greater adhesion orbonding strength. These characteristics will continue to be desirable incertain diaper applications, disposable pads, and in other products.There is a continuing need, however, to prevent migration of moistureand particles along the beads, i.e. along the length or in the machinedirection of the product.

Accordingly, it is one objective of this invention to provide animproved fine line adhesive application which prevents moisture orparticle migration to undesirable outlets at the line ends.

A further objective of the invention has been to provide apparatus forapplying an improved adhesive application to a substrate.

A further objective of the invention has been to provide an improvedarticle comprising a flexible backing sheet and an absorbent pad adheredthereto with fine lines of adhesive.

A further objective has been to provide an improved method for securingfluff to a flexible backing.

A further objective of the invention has been to provide an improvedmethod for adhering one substrate to another.

A further objective of the invention has been to provide an improvedmethod for applying adhesive to a substrate.

To these ends, a preferred embodiment of the invention includes anadhesive application comprising a plurality of parallel beads or fineline deposition of adhesive along a substrate in a machine direction,and a swirl pattern or random fibrous adhesive deposition in across-machine direction on the substrate at intermittent, selecteddistances along the fine line deposition. The swirl or fibrousdeposition joins the fine lines and provides a migration barrier acrossthe fine lines.

A fine line applicator, having a plurality of fine line or elongatedbead producing nozzles, is provided with air jet means associated witheach nozzle. These are intermittently activated to selectively swirl ordisrupt the emanating bead into a swirl pattern or into a random fibrousorientation, thus producing a homogeneous or continuous adhesive bandacross the fine lines. This band serves as a barrier to migration alongthe lines.

An air source is selectively controlled so as to discontinue air flow tothe air jet means when fine parallel lines are to be deposited, and tosupply air flow at selected times when desired to produce a transverseband of swirl pattern or random fibrous adhesive to seal off the finelines.

These sealing bands are produced, for example, in the areas which willrespectively form the leg holes or waist of a diaper to preventmigration of moisture or particles from between the backing and thefluff. At the same time, the enhanced bonding characteristics of thefine line adhesive are attained, yet without the need to otherwise treator apply additional components to stop deleterious migration.

Accordingly, a fine line applicator for depositing fine lines ofadhesives is provided with cyclic air jet means to produce swirls orfibrous depositions cross-joining the fine lines at selectedintermittent locations.

The invention provides advantages of both prior and previously exclusivetechniques, i.e. the adhesion benefits of fine line deposition with themigration preventing continuous adhesive blanket deposition.

These and other advantages will become readily apparent from thefollowing description of a preferred embodiment of the invention andfrom the drawings in which:

FIG. 1 is a perspective view of an adhesive application process,application apparatus and article according the invention;

FIG. 1A is a diagrammatic end view of the adhesive applicator of FIG. 1illustrating fine line adhesive deposition;

FIG. 1B is a diagrammatic end view of the adhesive applicator of FIG. 1illustrating adhesive swirl or random fibrous deposition;

FIG. 2 is a schematic elevational end view of the adhesive applicatortaken along lines 2--2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 but showing the fine line producinggrooves in the adhesive applicator; and

FIG. 4 is an enlarged cross-sectional view taken along lines 4--4 ofFIG. 2 and illustrating also an adhesive receiving substrate.

SPECIFICATION

Turning now to the drawings, it will be appreciated that the inventioncontemplates improved methods and apparatus for producing an improvedlaminate structure, particularly useful in the manufacture of disposableproducts, such as absorbent diapers, pads and other similar products.The manufacturing process for the laminate is diagrammaticallyillustrated in FIG. 1.

An applicator head 10 is operable to supply adhesive to one side of anelongated web comprising a flexible backing 11, such as a thin, moistureimpervious, polyethyene film. The moving web is then rolled through anip at 12, where a web 13 of absorbent fluff material is combined withthe backing web, such that the adhesive holds the two webs together.Thereafter, the combined moving laminate 14 is conveyed in a machinedirection to a cutting platen 15. A knife 16 severs the laminate withinthe area defined by crossbands of adhesive as will be described. Whilethe laminate 14 and the cut-off articles 17 are shown in FIG. 1 as beingrectangular, it will be appreciated they could be of other longitudinalshapes, such as diapers with cut out leg holes or other padconfigurations or the like.

It will also be appreciated that the fluff 13 is preferably a non-woven,absorbent material, such as that utilized in disposable diapers, forexample, but could be other forms of material, depending on the desiredapplication.

The invention contemplates the application of adhesive by the applicatorhead 10 onto the first web or substrate 11, primarily in a plurality offine lines of adhesive 20, as shown in FIG. 1. These are deposited ontothe substrate 11 from a slot die nozzle 21. Adhesive emanates from theslot die 21 in the form of a plurality of adhesive beads, such as at 22(see FIG. 1a). When the beads contact the moving substrate 11thereunder, they are deposited on that substrate in the form of aplurality of parallel, fine lines of adhesive 20.

It will be appreciated, as used above, the term "beads" is used fordescriptive purposes in this application to refer to the adhesiveemanating from the slot die nozzle 21 in the area between the slot dienozzle and the substrate 11. On the other hand, the term "fine line" isused generally in this application to describe the adhesive as it isdeposited on the underlying substrate 11. This distinction is made inthis application for the purpose of description only. It will beappreciated that the elongated parallel strips of adhesive on thesubstrate 11 could also be referred to as beads of adhesive on thesubstrate.

The slot die nozzle 21 is provided with means for intermittentlyagitating the beads 22 (FIG. 1A) into a swirl or a random fibrouspattern, as illustrated diagrammatically in FIG. 1B. Such agitated beadsare diagrammatically indicated at 23 in FIG. 1B. When the beads areagitated, they still descend to, and are deposited on the substrate 11,but not in the form of parallel fine lines of adhesives. Instead, theagitated beads commingle in a swirl pattern or in a random fibrousorientation. Such swirl or random fibrous lines constitute acontinuation of the fine parallel lines, but are intermingled with eachother so as to join the adjacent parallel fine lines in a band ofadhesive 24. Such bands are selectively and intermittently spaced in thecross machine direction, i.e. across the web 11, transversely to themachine direction.

When the beads 22 are deposited in parallel, fine lines on the substrate11, the parallel fine lines 20 are spaced apart and define channelstherebetween. Nevertheless, the intermingling of agitated beads 23 inthe swirl or fibrous pattern of the band 24 seals off the spaces orchannels between the fine lines 20 so that no particles of fluffmaterial or other particles can migrate along those fine lines past theband 24. Accordingly, the bands of adhesive 24 serve to interrupt anymigration of particles along the substrate 11 in the areas between thefine lines 20 of adhesive.

It will be appreciated that when the laminate 14 is cut by knife 16,that cut is disposed within the band 24, so that each end of theseparated laminates 17 have an edge band of intermingled swirled orfibrous adhesive extending in a cross machine direction across the endsof the fine lines 20. This interrupts any migration of particles betweenthe fine lines 20 outwardly at the edge 18 of the cut-off laminates 17.

It will also be appreciated that when the adhesive beads emanating fromthe nozzle 21 are swirled or otherwise agitated to form a random fibrouspattern, they still constitute a continuation of the lines of adhesivewhich are already laid down on the substrate 11, so that a migrationbarrier is formed by that band across the adhesive lines.

Turning now to a further description of the apparatus for producing theparallel fine lines of adhesives with the intermittent cross bands,reference is made to FIG. 2, which constitutes a diagrammaticelevational end view of the adhesive applicator 10. The applicator 10includes a head 30 and a slot die 21. With the exception of the detailsof FIG. 4, the applicator 10 is essentially like that described indetail in U.S. Pat. No. 4,874,451. Reference is also made to U.S. Pat.No. 3,825,379, and the melt blowing die disclosed therein.

The slot die 21 includes a plurality of adhesive grooves or nozzles 31,defined by complimentary relieved areas in die halves 32 and 33. Theadhesive outlet grooves 31 may be ganged in sections, such as sections34, 35 (FIGS. 2 and 3) for the generation of a plurality of adhesivebeads. These sections can be controlled independently, as described inU.S. Pat. No. 4,874,451 for particular applications.

Each section 34, 35 is fed by a respective inlet passage such as at 36or 37. Adhesive is conveyed from an adhesive control valve, such as 38,39, 40 or 41, to respective sections also as described in U.S. Pat. No.4,874,451. Valves 40, 41 feed respective sections 34, 35 shown herein.The inlets 36, 37 feed respective triangular portions 42 or 43 fordistribution of adhesive to the adhesive outlets 31. Referring to FIGS.3 and 4 then, each of the sections of adhesive emanating grooves 31 arefed by a respective triangular section 42, 43. Inlets 36 and 37 feed thetriangular relieved areas 42 and 43. The inlets are also connected tothe runners or passages 51, 52.

The valves 38-41 are operated through a valve air manifold 45 by one ormore air solenoids 46-48, as described in the preceding U.S. Pat. No.4,874,451. Recirculation valves 49 and 50 are used as described in saidpatent for adhesive control when the outside sections or banks oforifices are to be shut off, such as when the underlying substratemoving under the slot die is in an area corresponding to the positionwhere leg holes will be cut out from the resulting diapers.

It will be appreciated that the valves 38-41 are appropriately connectedvia manifolds and passages to control circuits for operating the valves,such as air passages, and to adhesive manifolds for selective control ofadhesive flow to the sections of adhesive emanating grooves or nozzles.

The slot die 21, according to the invention, is provided with air jetmeans 55, 56, defined as elongated passageways in manifold covers 57 and58. Air chambers 59 and 60 are interconnected to a source of pressurizedair 61 through a pneumatic line 62. Pressurized air source 61 iscontrolled by an electric or pneumatic solenoid controller means 63 ofany suitable type for operating the air source to selectively pressurizeline 62 and chambers 59 and 60 with pressurized air. When pressurized,this causes a flow of air through the air jet means or passages 55, 56,to impinge on a bead of adhesive 23 emanating from the outlet 31 (FIG.1B) to agitate that adhesive bead and cause it to form a swirl orspiral, or to be deposited in a random fibrous orientation across thesubstrate 11 in a band of adhesive 24, such as shown in FIG. 1. Itshould be appreciated that the air jet means 55, 56 impinge tangentiallyon the bead in one form, and may themselves be angularly oriented, suchthat their axes do not intersect, but are directed to cause the bead toform a spiral such as, for example, the air jets in U.S. Pat. No.4,983,109.

Of course, the air jet means 55, 56 can be provided in any suitableorientation to cause the desired swirl or agitation to produce a randomfibrous pattern in a cross band, as illustrated in FIG. 1. For example,air jet means such as that described in U.S. Pat. No. 4,815,660, U.S.Pat. No. Re. 33,481, or in applicant's co-pending application Ser. No.07/783,989, filed Oct. 29, 1991, could be used. Also, any other form ofmeans to selectively intermittently agitate the adhesive emanating fromthe outlet 31 to cause it to deposit to seal off the gaps between thelines on the underlying substrate could be used. For example, acone-shaped air passage with vanes for swirling the air and surroundingthe adhesive orifice could be used, as well as elongated air slots orother means.

It will be appreciated that the band of adhesive, which is deposited onthe substrate 11 when the air jets are operated, is in the cross machineor transverse direction across the substrate. The agitated beadsthemselves are simply a continuation of the adhesive lines which arealready deposited on the substrate. The swirls or fibrous pattern in theband 24 intermingle with adjacent adhesive beads and/or lines ofadhesive on the substrate, so as to bridge the spaces or distancesbetween the parallel fine lines of adhesive, which were being depositedbefore the flow of air was initiated, in order to close off any spacesbetween those fine lines. In the deposited pattern, this interrupts anymigration of particles along those fine lines between the adheredlaminate substrates 11 and 13.

Of course, it will also be appreciated that the control means 63 isoperated to intermittently pressurize the chambers 59, 60, tointermittently cause air flow through the air jet means 55, 56. Thetiming of these intermittent applications of air to the bead from thejets 55, 56, is predetermined so that the generation of the bands 24 inthe cross machine direction on the substate 11 are deposited in thoseareas of the substrate which will be cut by the knife 16 (FIG. 1).

Also it will be appreciated that such transverse or cross machinedirection bands can be generated at other predetermined positions. Whendiapers are made, for example, these bands can be oriented in the areassurrounding the web material where the leg holes are to be cut. Thisinterrupts migration of particles outside the edge of the laminate atthose particular areas.

Accordingly, it will be appreciated that the invention providesapparatus and methods for depositing a predetermined adhesive on asubstrate and for producing a laminate of two substrates with animproved adhesive disposition therebetween.

Accordingly, one substrate is adhered to the flexible backing substrate11 by means of elongated, parallel fine lines of adhesive, which produceexcellent bonding characteristics of the one substrate to the other,while at the same time the intermittently spaced bands 24 serve to jointhe elongated adhesive lines and to interrupt any migration or particlestherealong. Manufacturing, cutting or other processes can be carried outin the area in which the bands 24 are deposited, to prevent themigration of particles of non-woven material of the substrate 13, forexample, outside the edge of the finished laminate article at the edge.Accordingly, the article exhibits good bonding characteristics providedby a parallel fine line adhesive process, without the disadvantage ofparticle migration or the necessity to conduct other furthermanufacturing techniques or add additional elements to the laminate.

It will be appreciated that the structure of the slot die can be likethat as shown in U.S. Pat. No. 3,825,379, with the appropriate slotwidths to produce the desired fine lines of adhesive on an underlyingsubstrate when the air is turned off, according to the invention herein.

It will also be appreciated that the invention is useful in a system,such as that disclosed in U.S. Pat. No. 4,874,451, where it is desiredto provide a band of adhesive in the cross machine direction to join orseal off the ends of the fine line adhesive applied to the substrate.This occurs in one application such as diapers, in the areas to comprisethe waistband and the leg holes of the diapers.

Accordingly, the invention provides for the realization of the greateradhesive and bonding characteristics of the fine line adhesivedeposition process, but also provides the benefits of the swirl orrandom fibrous pattern process all in the same laminate by selectivelycontrolling the application of air to the slot dies which are operableto emanate a bead for fine line deposition. The swirl or random fibrousbands can be created at any predetermined areas on the substrate.Moreover, instead of being continuous across the substrate, such bandscould be formed in any pre-selected length by separating the airchambers 59 and 60,and dedicating them respectively to air jets servingeach groove 31. With appropriate valving, this can be used to cause thebead emanating from that groove to swirl or move randomly, or to depositin a straight line. Finally, it will be appreciated that while the swirlpattern or a random fibrous orientation may be preferred, either ispossible, depending upon the orientation of the air jets 55, 56 and thenature of the air jet flow. Other forms of intermittent agitation, suchas mechanical or other expedients, could be utilized as well to causethe emanating beads to intermingle, at least as deposited on thesubstrate, to produce the band 24, as described herein.

Accordingly, these and other modifications and advantages will bereadily apparent to one of ordinary skill without departing from thescope of the invention, and the applicant intends to be bound only bythe claims appended hereto:

I claim:
 1. A method of applying adhesive to a substrate for use inlaminating the substrate to another component and comprising the stepsof:depositing a plurality of substantially parallel lines of adhesiveonto a substrate; and intermittently agitating said adhesive lines priorto deposition on said substrate to cross-join parallel lines of adhesivedeposited on the substrate to form bands of adhesive at spaced locationsacross said parallel lines.
 2. A method of adhering two substrates toform a laminate article including the steps of:depositing a plurality ofsubstantially parallel lines of adhesive on a first substrate;intermittently disturbing the depositing of parallel lines of adhesiveto cause the adhesive to form an adhesive band across said lines inpredetermined locations on said first substrate; and combining a secondsubstrate to said first substrate with said adhesive lines and bandstherebetween, bonding said substrates together with said bandspreventing migration of particles intermittently along said lines.
 3. Amethod for manufacturing a laminate for use in making disposable diaperscomprising a flexible backing and fluff, the method comprising the stepsof:depositing a plurality of parallel lines of adhesive on a webcomprising said backing; intermittently interrupting said depositingstep and causing said adhesive to intermingle between said lines toproduce an adhesive band across said lines in predetermined locations onsaid backing; and combining said fluff with said backing with saidadhesive therebetween bonding said fluff to said backing, said adhesivebands interrupting migration of particles along said lines.
 4. A methodof adhesively combining two substrates including the steps of:operatinga plurality of nozzles to produce a plurality of beads of adhesive;depositing said plurality of adhesive beads on a first substrate in aplurality of parallel lines of adhesive thereon; intermittentlyagitating said beads as they emanate from said nozzles to interminglesaid beads and to deposit on said first substrate a band of adhesiveacross said lines; and combining a second substrate onto said firstsubstrate with said adhesive bonding said substrates together.
 5. Amethod as in claim 4 wherein said agitating step includes intermittentlyimpinging on said beads at least one air stream to swirl said beads intoa spiral to deposit an adhesive pattern of overlapping swirls acrosssaid first substrate.
 6. A method as in claim 4 wherein said agitatingstep includes intermittently impinging a flow of air on said beads toproduce a band of random fibrous adhesive lines across said substrate.